Measured-service telephone system



Oct. 11, 1927. 1,644,968

J. WICKS MEASURED SERVICE TELEPHGNE SYSTEM Original Filed May 25. 1921 4Sheets-Sheet l N s s \L LR lq A m @PIP q 1% l CQZQCJ'IF Il Q lily/mw j Ql j M flu-gp 1927. Oct 11 J. wlcKs MEASURED SERVICE TELEPHONE SYSTEM 4Sheefs-Sheet Original Filed May 25. 1921 m um@ -Inuen m7- f Jhn HunksOct. 11,1927.

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J. WICKS MEASURED SERVICE TELEPHONE SYSTEM Oct. 11, 1927. 1,644,968

original Filed May 2:3.'1921 4 sheets-sheet 4 Jahn MURE mengen oet. 11,1927.

UNITED STATES PATENT i oFElcE.

JOHN WICKS, OF OAK PARK, ILLINOIS, ASSIGNOB, BY MESNE'ASSIGNMENTS, T0AUTO- MATIC ELECTRIC INC., OF CHICAGO, ILLINOIS, A CORPORATION OFDELAWARE.

MEASURED-SERVICE TELEPHONE SYSTEM.

Application 'led Hay 23, 1921,.8er1a1 No. 471,775. Renewed January 5&2,1826.

4The present invention relates in general to v measured servicetelephone systems, and more. particularly, vto automatic measuredservice systems of the type in which aystation apparatus is provided ateach su scribers'station requiring the deposit of a coin for eachsuccessful connection In one well known arrangement, thecalling deviceat the subscribers "substation is normallyinoperative to controll thecentral olice switches and it is 'only by first deposit-f ing a cointhat the subscriber is enabled to render his sender operative to controlthe. switches in the exchange to set up ay connection. Thereafter thecoin deposited is either collected or refunded depending upon whetherthe subscriber called responds or not. If the party called is anoilicial of the telephone company or an operator the coin is refunded inany case.

Certain improvements have been devised in the above mentioned systemwhereby a calling subscriber must deposit a coin before making a callprovidedvv he desires aconnection -with another subscriber, while if hedesiresl a connection with an operator no coin is required to bedeposited. A particular object of the inventionis to provide newcircuits for a type of repeater which is used in such an improvedsystem'whereby the operationsfof the switch are rendered more positiveand the impulsing circuits through the repeater are greatly improved. Aspecial feature incorporated into this repeater circuit is anarrangement so that if a recordino operator is called .she is given adiscriminatlng tone in order to inform her whether the callingsubscriber is limited as to certain vservices or connections.

'According to another feature in the repeater if a calling subscriberlattempts to make a connection with another subscriber without firstdepositing a' coin he is unable to do so and he cannot, without firstreplacing his receiver, loperate the central oilice switches beyond acertain point even if, aft/er attemptin to extend a connection, hedepos1ts t e required coin. This provision, of course, eliminates thepossibility of wrong numbers being called on account of one 4or moredigits being absorbed. a

Still another feature of the invention is to so arrange the repeatercircuits that the trunk selecting o erations of the subscribersy rotaryline switc es which have access to the repeaters are rendered much morepositive a repeater not function properly or the c 'oin collectingmechanisml and subscribers subi station not be inpro er condition, analarm is given to the atten ant, who may then ascertain 'what is thetrouble. v

l Another feature of the invention relates to the provision of a meteroneach subscribers line Whichregisters each completedcharged call. Thisprovision. is made so thatl a checkmay be had against the amount ofcoins collected by the subscribers paystation apparatus.

Still another feature relates to 'the' rowhereby theoperation of theconnector in selecting an idle line in a group of lines is rendered morepositive. y

There are certain Iother features of the invention not now specificallymentioned which Will be described together with the foregoinghereinafter with reference to the accompanying drawings. v g Referringnow to the drawings comprisin Figs. 1 4, inclusive, the general scheme'o the system shoWn-th'ereinjmay be briefly dey scribed as follows: Thesubstation A, Fig.

l, is ofthe ordinary .automatic type having the usual talkinginstrumentalities, and an impulse sender S `Being a-measured servicesubstation there is also provided a well known type of coin collectingmechanism which may be of the type shown' and dey scribed in the-U.S..patent toForsberg No. 1,043,219, granted Nov. 5, 1912.

The line 'conductors 11 and' 12 extend from" the subscribers' substationtothe exchange terminating at the lat-ter point in an individualtrunkselecting or ,line switch C. This switch is of the well knownrotary ty e in which the wipers have no normal position.

always remaining in engagement with the bank contacts associated withthe trunk line last used; and whose function is to extend the line whencallin to a trunk line which ter u minates in an id e first selectorswitch. One of the trunk lines to which theline switch C, in common witha plurality of other line switches, has access isshown extending to thefirstl selector E', Fig. 3. The relay equipment in Fig. 2 indicated byreference char-` acter D is a repeater, there being one such repeaterinserted in each first selector trunk. At T is shown a discriminatingtone machine whose function is to give a discriminating tone to arecording operator should one be called by the subscriber, in order toinform her of his status, that is, whether. he is entilted to certainconnections or not.

Associated with the repeater are the alarm si al and supervisorycircuits shown in Flg. 2 which perform the function of noti- 1ng theattendant in the exchange imme iliately anything goes-wrong with therepeater D.

The first selectors are the first in the series of numerical switcheswhich may comprise first selectors, second selectors, and connectorswhich are used to complete connections between calling and called lines.One of these rst selectors is shown at E, Fig. 3. This switch is of thewell known Strowger vertical and rotary type and has access to trunklines extending to second selectors such as E2 or E8. The secondselector E2 is similar to the rst selector E', as is the second selectorE, However, the circuits nf the second selector E3 differ slightly fromthose of the other two switches and this will be explained shortl Therotary connector i-I, Fig. 4, is one of the connector switchesaccessible to the second selector E8 and is of the well known Strowgervertical and rotary type which may be seized by means of a secondselector in order to complete a connection to a called subscriber suchas the one shown at A. This connector is capable of selecting an idleline in a group of lines or if all the lines in the group are busy tonotify the calling subscriber of this fact. .The substation A is one ofthe substations to which the connector H has access and may be similarto the one shown at A, although, for convenience, the measured serviceequipment has been omitted.

It is customary in automatic exchanges to provide a special group ofsecond selectors through the medium of which a calling subscriber mayconnect with the various .groups of trunk lines extending to thediferent operators and employees of the telephone company, such forexample, as the information operators, trouble operators, recordingoperators, or the wire chief. The special second selectors are generallyaccessible from a certain level in the regular first selectors. In Fig.3 a trunk line is shown which terminates in a set of bank contacts in alevel of the first selector E and which extends to the second selectorE2. The second selector E2 is one of a group of special second selectorswhich have access to the roups of trunk lines above referred to.

ne of these trunk lines is shown in the drawings and terminates in therecording operators equipment indicated by the reference character Cwhich comprises a group of relays, an induction coil, an answering jackJ, and a call signal lamp L.

In order to ex lain the operation of the circuits it will rst be assumedthat the subscriber at substation A desires to call the recording oerator at the equipment O, it being ossi le to accomplish thisconnection without de ositing a coin as was mentioned hereinbe ore. Whenthe receiver is removed at substation A the line relay 26 of theindividual line switch C is energized over the two sides of the callingline in series. Relay 26 upon operating, at its armature 4() completes acircuit which includes the switching relay 25 and the motor magnet 27 inseries and at its armature 39 connects the test wiper 46 to the abovecircuit at a point midwa between the switching relay and the sai motormagnet. The operation of the line switch C de ends upon whether thetrunk line with which its wipers 44-47, inclusive, are in engagement isbusy or not. Assuming this trunk line to be busy there will be a groundpotential present upon the test contact engaged by the test wiper 46,the switching relay 25 will be short circuited and the motor magnet 27being supplied with direct ground via the said test wiper will operateas a buzzer to advance the switch wipers step by step in search of anidle trunk line. However, it will be assumed in the present case whenthe receiver is removed at substation A the switch wipers 44-47,inclusive, are in engagement with the bank contacts associated with anidle trunk line. Under these conditions, immediately following theenergization of the line relay 26 the switching relay 25 not being shortcircuited will ener ize. Upon energizing, relay 25 disconnects t e lineconductors 11 and 12 of the calling substation from the Winding of theline relay 26 and from ground, respectively, and extends them by way ofarmatures 33 and 36, wipers 44 and 47 bank contacts 52 and 55,conductors 48 and 5l, armatures 145 and 144 and their resting contacts,armatures 160 and 164 and their resting contacts, windings of thedifferential relay 130, and thence through the winding of the line relay135 and impedance coil 139.

The line relay 135 of the repeater D is energized over two sides of thecalling line in series and at its armature 183 completes the circuit ofslow acting relay 136. The latter relay upon energizing, at armature 186places ground on release trunk conductor 50 by way of the retardationcoil 138 thereby establishing a holding circuit for line switch C whichextends by way of bank contact 54, test wiper 46, armature 35 and itsfront contact, through the winding of the switching relay 25,. andthence through the winding of the,

ing line relay 26 has had time to deenergize.

, the winding of the-motor magnet 27 to battery. It will beunderstood't-hat this holding circuit is completed before the slow `act-A branch of the holding circuit also extends by way ot the privatenormal conductor 30 to the multipled test contacts in the banks ofconnector switches which have access to the line of the substation Awhereb the said line. 'is protected from intrusion 1n a well knownmanner. It will be remembered that ground is supplied to thereleasetrunk conuctor 5,0 through the xatardation coil 138.

This coil is of very low. resistancev say of about 2% ohms so that themultiples of the test contact `ltaccessible to the other line switchesarel made busy. Relay 136 upon I energizing, also completes a circuitfor the polarizmg winding ot the electropolarized rela 132 and that Vofthe polarizing winding of 't e relay 128, in series with the windingv ofrelay 141. The electropolarized relays 128 and 132 are so adjusted thatcurrent kiow- `ing in theirpolarizing windings does not cause theselrelays to operate their armatures, though after once operating thecurrent flow in the polarized windings Iis lsuihcient to maintain thearmatures attracted. Relay 141 is therefore the only relay operated overthe above traced circuit. Relay 141, upon energizing, opens a' point ina certain shunt circuit which will be described later.

When the line relay 135 of the repeater D energizesa bridge isclosedacross the trunk conductors 200-202, which may be traced asfollows: armature 190 and its back con. tact, upper winding of theelectropolarized 'relay 132, normally closed springs controlled byarmature 172, normallyclosed springs controlled by armature 160, upperwinding of the electropolarized relay 128, lower windi ing of the relay133, front contact and arma- `lture 184, normally closed springscontrolled by armature 164i, normally closed springs controlled barmature 173 to trunk conductor 202. v pon the closure of the abovetraced circuit the line relay 225 of the first selector E is energized.Upon operating,4

relay 225 completes the circuit of the slow actingrelease relay 226which immediately' operates to prepare the operating circuits of theselector E at armature 238 and at armature 237 places ground on therelease trunk conductor 201 through the resistance 240. This groundextends back over the release trunk conductor 201 tothe polarizing Windiings of the relays 128 and 132.

Therelay 141 is not shortfcircuited at this time as the resistance 240is high enough to prevent the 'relay winding from beingv shunted: .thus

ground is now supplied-to the polarizing windings of relays 128 and 132from first selector E .and from the repeater'D.

Before proceeding further with the eX-' planat-ion. attention is calledto a shunt cir- -succeeding switches.

cuit aroundarmature y184 and its front contact which, 1t may bementioned, are the impulse springs of the repeater D which conf springsrepresented y armature 184 and its working Contact inrepeating impulses.

"The calling subscriber yat substation A may now operate his callingdevice'in accordance with the two digits which it 1s necessary to callin order tofobtain connection 4 with the recording operator. By theopera? tion of the calling'device S a series of'interru'ptions isproduced in the circuit of the linerelay .135 thereby lcausing thisrelay to deenergize in response to such interruptions, each time openingthe previously traced circuit ofthe line relay 225 ofthe first selectorE."; At the first deenergization of relay 135 an impulseof current issent to the slow acting relay 137 whichis energized and remainsenergized throughout the series of impulses. yRelay 137, uponenergizing, completes a circuitv extending fromground by:

way of armaturel191 and its front contact, normally closed springscontrolled by arma-v ture 167, and thence vthrough the winding of therelay 129 to battery.` Relay 129 is energized over thiscircuit and, uponoperating, establishes a locking circuit for itself at armature 167 andat armatures 165- and 168short circuits the windings ot the differ#ential relay 'Which was previously in-V cluded in the circuit of theline relay 13 5. By this operation the line relay is given a much betterimpuls'ing circuit. Another result of the energization of relay 137 isthat at armature a-direct bridge is placed across the trunk conductors200 and '202 which does not include the windings of the electropolarizedrelays 128, 132, and the lower Winding of the relay 133. These circuitclianges aremade in order to'reduce the resistance and impedanceof'theswitchv control circuits to a` minimum during the transmission ofimpulses. Proceeding now tothe operation of the lirst selectorvE, ateach deenergization of the line relay 225 an impulse of current is sentto the verticall magnet 232 in series with the slow acting.

relay 227. Magnet 232 operates to raise .the

i switch wipers 2554257, inclusive, step by step until they are'placedopposite-the level of bank contacts in which are terminated tru linesleading to the special group of seco 1d selectors which have access totrunk lines leading to operators positions. The slow acting relay 227 isenergized in series with the vertical magnet and maintains its armatureattracted throughout the vertical movement of the switch. Upon the firstvertical step of the switch a circuit is completed extending from groundon release trunk conductor 244, armature 245 and its front contact, offnormal spring 241 and its working contact, and through the winding ofthe stepping relay 228 to battery. Relay 228, upon energizing,establishes a locking circuit for itself at armature 247 and at armature248 prepares the circuit of the rotary magnet 231. .At the terminationof the vertical movement of the switch, the slow acting relay 227 isdeenergized andthe circuit of the rotary magnet 231 is completed. Magnet231, upon operating, rotates the switch wipers into engagement with thefirst set of bank contacts in the selected level and at armature 254opens the locking circuit ot the stepping relay 228 which deenergizesopening the circuit of the rotary magnet 231 which deenergizes also. Thefurther operation of the selector E depends upon whether 0r not thetrunk line with which the Wipers 255-257, inclusive, are now inengagement is busy. Assuming this to be the case, there will be a groundpotential present upon the test contact engaged by the test wiper 256and a circuit will be completed extending from the said grounded testcontact by way of the test wiper 256, armature 251 and its back contact,armature 254 and its back contact, off'normal spring 241 and its workingcontact, and through the winding -of the stepping relay 228 to battery.Upon energizing, relay 228 establishes a locking circuit for itself andcompletes the circuit of the rotary magnet 231. This alternate operationof relay 228 and the rotary magnet 231 will continue until the switchwipers 255-257, inclusive, are rotated into engagement with the bankcontacts associated with an idle trunk line `which we will assume arethe bank contacts 260-262, inclusive. As this trunk line is idle therewill be no ground potential present upon the test contact 261 engaged bythe test wiper 256 and no circuit will be completed for the steppingrelay 228. The switching relay 229 will now be energized in series withthe stepping relay 228 as it is no longer short circuitcd. It may bestated at this point that the switching relay 229 is of such highresistance that the stepping relay 228 is not energized in series withit. Relay229, upon operating, disconnects the incoming trunk conductors200 and 202, from the windings of the line relay 225 and extends them byWay of armatures 250 and r253, wipers 255 and 257, bank contacts 260 and262, trunk conductors 267 the slow acting release relay 281. The latterrelay, upon energizing, prepares the operating circuits of the selectorE2 at armature 292 and at armature 291 places ground on release trunkconductor 268 through the resistance 295 thereby establishing atlioldingcircuit for the switching relay 229 of the first selector E. This groundalso extends by way of the release trunk conductor 201 to the polarizingwindings of the relays 128 and 132 but as the resistance 295 is includedin this circuit the relay 141 is still maintained energized and theshunt circuit around the impulse springs 184 is open at armature 196.

The calling subscriber may now voperate his calling device in accordancewith the second and final digit in the number of the desired operatorthereby producing a second series of interruptions in the circuit of theline relay 135 of the repeater D which are repeated by means of thearmature 184 to the line relay 280 ot' the second selector E2. Theselector E2 is exactly like the selector E and its operation will not bedescribed in detail. lt will suflice to say that the switch shaft israised step by step until the wipers 310-312, inclusive, stand oppositethe level of bank contacts in which are terminated the trunk linesextending to the recording operators position after which the wipers areautomatically rotated in search of an idle trunk line. Assuming thatthev trunk line shown in the drawings is the first idle trunk line theswitch wipers will nally be brought to rest in engagement with bankcontacts 313-315, inclusive, whereupon the switching relay 284 will beenergized. As a result of the energization of relay 284, the trunkconductors 267 and 269 are disconnected from the windings of the linerelay 280 and are extended by way of wipers 310 and 312, bank contacts313 and 315, to the upper and lower windings of the double Wound relay320. Relay 320 is therefore energized and completes a circuit for theslow acting relay 321 which, upon energizing, in turn closes the circuitfor the lamp signal L and also completes the usual holding circuit forthe selectors E and E2 which may be traced as follows: ground by way offront contact and armature 328, through the primary Winding of theinduction coil I', through the resistance 316, bank contact 314, testwiper 311, armature 306 and its front contact, where it joins theholding circuit previously described. The switching relays 284 and 229are maintained energized and' the switches E and E2 are accordingly heldin their operated positions.

scriber is entitled to, after operating the listening key in the cordcircuit, the recording operator will throw the key K. By this operationthe secondary of the induction coil lis connected in bridge of the trunkconductors and the discriminating tone on the c release trunk may beheard by the recording operator over a circuit which includes thesecondary of the induction coil l. Ilhe primary of the induction coil llis energized over a circuit which extends as `follows: from thediscriminating tone machine T, terminals 32 and 31, private normalconductor 30, front contact and armature 35, test wiper 46, test contact5ft, release trunk conductor 50, condenser 144:', conductor 201, frontcontact and armature 251, test wiper 256, test contact 261, releasetrunk conductor 268, front contact and armature 306, test vwiper 311,test contact 314, resistance 316,

through the primary inductioncoil I', and armature 328 and its frontcontact, to ground. It will be noted that in the above circuit there isanother path for the current from the tone machine T to take, which maybe traced from the conductor 50, through the winding of the retardationcoil 138 to ground, by way of armature 186 and its iront contact.However, as this circuit includes the winding of the retardation coil138 the greater part of the current from the tone machine flows over thepreviously traced circuit. The class of service to which the callingsubscriber is entitled is determined by the particular tone whichl isconnected to the private normal conductor of his line and which isinduced in the secondary of the induction coil I and is audible to therecording operator. As soon as the recording operator determines theclass of service that the calling subscriberis entitled to she willrestore the key Ky to normal -so as to communicate'with the callingsubscriber. The recording operator may now converse with the callingsubscriber 1n order to ascertain his desires. The talking circuit may betraced over the heavy talking conductors and it will be noted that thereisa bridge across vthe talking circuit in the repeater which includes awinding of the electropolarized relay 128 and the lower winding of therelay 133. The lower winding of the relay 133 operates asa retardationcoil sov that the v transmission eiliciency of the talking circuit isnot materially affected by the above mentioned bridge. From thispointon, the

operation may take any desired course, dependin upon the wants of thesubscriber, and wi l not,be described. Disconnection is eected in theusual manner by the han ing up of the receiver at substation A. 'hisoperation causes the relay 135 in the repeater' D to deenergize with theresult that the slow acting relay 136 of the re eater is deenerg1zed todisconnect groan from the holdu ing circuit of the line switch C. Relay135, upon deenergizing, also opens the bridge across the trunkconductors 200 and 202, with the result that the relay 320 at therecordmg operators position is deenergized followed by thedeenergization or the slow acting relay 321. The switching relays in theselector switches E' and E and in the line switch C are deener ized andthese switches are thereby restore to their normal position in the usualand well known manner. The operations in the repeater D which take placeu ondisconnection and which have to do wit the collection and refundingoi coins are of no importance in the case of the connection justdescribed and will therefore be explained later on.

The operation of the system when the sub- .scriber at substation Adesires connection with another subscriber will now be described it rstbeing assumed that the subscriber at substation A. attempts to makeconnection with the desired partys line without first depositing a coinin his paystation apparatus.

When the receiver is removed at the substation A the o erations by whichthe line of the calling subscriber is extended through the medium of theline switch C and the repeater D to a first selector E are identicalwith the operations described in the previous case and will not berepeated. The operation of the selector E" wherein the connection isextended to a second selector likewise alreadyV have been described andin this casel there is nothing new in the operation except that thewipers 255-257, inclusive, are ralsed oppor site a bank level in whichare terminated trunk lines extending to second selectors of the regulartrunking system. The second selector E is a switch of this class and itwill bel assumed that the trunk line extending thereto isthe rst trunkline found to be idle and that the selector E establishes connectionwith the bank contacts 265-267, inclusive. The trunk 'conductors 200 and202 will now be extended by the operation of the switching relay 229 bywayof wipers 255 and 257, bank contacts 265 and 267, to the ing-itsarmature 275 relay 271 closes a hold-4 ing circuit which extends asfollows ground by way `01E armature 275 andA its front contact, testcontact 266, test wiper 256, to armature 251 and its front contact,where the circuit divides, one path extending'through the winding of theswitching relay 229 and the interrupter relay 228 in series to battery,and the other ath extending by way of release trunk con uctor 201 tojunction oint 198, Where it joins the branch exten ing from round andfront contact of armature 188 in ghe repeater .D. It will be observedthat the above traced circuit contains no resistance such as resistances240 and 295 and, as a result, relay 141 in repeater D is practicallyshort circuited. This relay is therefore deenergized and atits armature196 closes the previously described shnt circuit around armature 184 ofthe line relay 135 and its front contact, thereby rendering the armature184 ineffective to open the bridge across the trunk conductors 200 and202 when the relay 135 is deenergized. When the calling subscriberoperates his dial in accordance with the next digit and roduces anotherseries of interruptions in t e line circuit the' result-ingdeenergizations of relay 135 will be of no eiect and it will be apparentthat the selector E3 cannot be operated.

The difference in the two classes of second selectorsl will now beapparent. All the selectors which are required to be used in extending aconnection to an o erators position or the line of an oilicial o thetelephone company are provided with resistance in their release trunkssimilar to the resistance 240 and 295, while those switches which areused only in connections to local subscribers have the resistanceomitted. It follows then, that whenever it is attempted to use a switchof the latter class, under the circumstances just described, where nocoin has been deposited, the relay correspon-ding to the relay 141 ofthe repeater in use will be short circuited vand will deenergize todisable the operating circuit exten ing to the switch thus preventingfurther extension of the connection.

The operation of the system in the case where the subscriber atsubstation A deposits a coin before calling the desired subscriber willnow be described and in this connection the process of collecting thecoin at the termination of the conversation will be briefly described.The first operation on the part of the subscriber at substation A is todeposit a coin of suitable denomination in the coin collecting mechanismprovided for that purpose. This mechanism is well understood and itsoperation need not be explained in detail. When the coin is deposited itdescends p-ast the trigger mechanism which is released by the coin withthe result that the polarized relay of the coin` collecting mechanism isconnected from the line conductors to ground. The coin is held insuspense by a trap door where it is adapted to be either collected orrefunded under control of the polarized magnet. The coin may bedeposited either before or after the receiver is removed. In either casethe latter operation brings about the operation of the rotary lineswitch C whereby the line is extended to an idle r'st selector switch.As= suming that the selector E', Fig. 3 is the switch to whichconnection is extended, the operations are the same as have already beendescribed and will not be repeated, Wit one exception, however; when theline conductors 11 and 12 are connected by the operation of the lineswitch C with the windin s of the line relay 135 and the impedanceco1ll39, of the repeater D, the ground on line conductor 12 unbalancesthe differential relay 130, which is included in the linecircuit, andcauses this relay to energize. It may be stated at this point that thepolarized magnet at the substation is of high resistance and does notmaterially interfere with the transmission of operating impulses or withthe talking circuit but it is nevertheless suicient to cause the relay130 to operate as described. Upon attracting its armature 170, relay 130closes a circuit for relay 134 which, upon energizing, establishes alocking circuit for itself at armature 178. Relay 134 also grounds theholding circuit extending back to the line switch C at its armature 179and at its armature 180 opens the shunt circuit around the impulsingsprings represented by armature 184 and its front contact. This latteroperation is an essential feature to be considered at this time forobviously it permits any of the switches in the exchange to be operatedno matter whether they are provided with resistance in the release trunksuch as the resistance 240 or not. Relays 130 and 134 thereforeconstitute means responsive to the deposit of the coin for rendering therepeater D operative to repeat impulses regardless of the type ofswitches which it is attempted to operate.

The calling subscriber may now operate his calling device in` accordancewith the digits in the number of the substation A. The selector E willrespond to the first digit in the same manner as has already beendescribed. The second selector E3 will also be operated in the usualmanner to the desired level in which are terminated trunk lines leadingto connector switches such as connector H, Fig. 4, which has access tothe line of the substation A. The selector E3 will then rotate in thewell understood manner to select a trunk line which leads to an idle oneof these connector switches and, which, it will be assumed, is the trunkline comprising conductors 380-382, inclusive, and terminating in bankcontacts 353-355, inclusive. As this trunk line is idle, there will beno ground potential present upon the test contact 354 and the switchingrelay 274 will be energized. Immediately upon the energization of relay274, the trunk con ductors 201 and 202 will be extended by way of wipers350 and 352, bank contacts 353 and 355, conductors 380 and 382, normallyclosed springs controlled by armatures 420 and 421, to the upper andlower windings of theline rela 401 `0:t` the connector H. Relay 401 wille therefore energized and will operate to complete the circuit of theslow acting release relay 402 which operates to prepare the impulsingcircuits of the connector H at armature 429 and at armature 428 placesground on the release trunk conductor 381 thereby establishing aholding' circuit for the selector switches E3 and E.

As before mentioned, immediately upon the first deenergization of theline relay 135 in the repeater D the slow acting relay 137 is energizedand the circuit oi the relay '129 completed. The latter relay, uponenergizing, establishes, a locking circuit for itself and short circuitsthe windings of the differential relay 130. By this provision it will beseen that should the calling subscriber attempt to extend the connectionwithout rst depositing a coin and then after linding that he gets noconnection deposits a coin he will be unable to affect the differentialrelay 130 without first hangingup his receiver. rEhis provision ismade'so that the .possibility of the calling subscriber obtaining Wrongnumbers by having one or more digits of the desiredcalled numberabsorbed on accountof the shunt circuit around the impulse springs 184,is entirely eliminated.

The calling vsubscriber at substation A i may now operate `his callingdevice for the response thereto.4 Atp each deenergization,

next "digit of the desired number. By this operation a series ofinterruptions is pro-l duced in the circuitvof the line relay 135 of therepeater D and these interruptions are then repeated by means of: thearmature 184 to the line relay 401 ofthe connector H which deenergizes aplurality of times in an. impulse of current is sent over a circuitextending from ground by way of armature 424and its back contact,armature 429 and-its front contact, o normal springs "436 and 437,winding of the slow acting relay 404, and thence through the Winding ofthe vertical magnet 413v to battery. .The

above Iis the circuit over which the iirst im 470473, inclusive, steplby step until they and maintains are placed opposite the level of bankcontacts in which is located the contact set associated with the line ofthe substation A. The slow acting relay 404 is energized in series withthe vertical magnet 413 its armature attracted throughout. the verticalmovement of the switch, and at the termination thereof deenergizestransferring the operating circuit to the rotary magnet 412.

The subscriber at substation A may now dial the next and iinal digit ofhis desired number. As before, a series of interrup tions is produced inthe circuit of the line relay 135 of the repeater D and these arerepeated to the line relay 401 of the connector H by means of armature184 and its front Contact. At each retraction of its armature 424 animpulse of current is sent to the rotary magnet over a circuit extendingfrom ground by way of the said armature and its back Contact, armature429 and its front contact, olf normal springs 436 and 438, armature 435and its back contact, back contact and armature 447, winding of the slowacting relay 407,` back Contact and armature 460, through the winding ofthe rotary magnet 412` to battery. The rotary magnet 412 operates torotate the switch wipers the set of bank contacts associated with theline of the substation A which, we will assume, are the bank contacts474-477, inclusive. llhe slow acting relay 407 is energized in serieswith the rotary magnet and at its armature 451 completes the circuit ofthe slow acting relay 408. .The latter relay, upon energizing, connectsthe test wiper 472 to the winding of the test relay 406.

Assuming that the desired line vis busy at the present time, there willbe a ground potential presentupon the test contact 47 6 engaged by thetest wiper 472 and the test relay 406 w'ill be energized. Relay 406,upon operating, prepares a locking circuit for itself atits armature 446which is completed upon the deenergization of the slow acting relay 408,and at its armature 448 places the busy tone on` the lower heavy talkingconductor whereby the calling subscriber is notified that the desiredline is busy and he will replace his receiver upon the switchhookthereby initiating the release of the operatedswitches in a manner whichwill be'described later. i

It will now be assumed that the line of the substation A is one of thegroup of lines listed under the same number.y The circuits of theconnector H must then be changed in order to enable it to select thefirst idle one of these lines. This is accomplished by connecting thetest contacts -similar to test contacts 475 and 476 together on allexcept the last line of the group.. Thus-` and thence a5 y 470-473,inclusive, into engagement with when a line becomes busy ground ispresent upon both these test contacts. Assuming that the test contacts475 and 476 are so connected and that the line of the sub-station A wasbusy when connection thereto.

was attempted by connector H the test relay 406 will be energized asbefore described md will operate to establish a locking circuit foritself at armature 446. Following the deenergization of the slow actingrelay 407, there being a ground potential present upon the test Contact475 engaged by the test wiper 471, a circuit may be traced eX- tendingfrom the said grounded test contact by way ofl said test wiper 471, backcontact and armature 450, armature 445 and its front contact, armature464 and its back contact, and thence through the winding of the steppingrelay 403 to battery. Relay 403 is energized over this circuit and, uponoperating, establishes a locking circuit for itself at armature 432 andat armature 433 completes the circuit of the rotary magnet. Magnet 412operates to rotate the switch wipers into engagement with the next setof bank contacts in the selected level and at armature 464 breaks thelocking circuit of the stepping relay 403 which relay deener` gizesopening the circuit of the rotary magnet 412 which deenergizes also. Theslow acting relay 408 is energized in multiple with the rotary magnetand operates to maintain the test wiper 472 into connection with thetest relay 406. If this next line is busy the test relay 406 will remainenergized, the stepping relay 403 will be again energized and theconnector switch wipers will be rotated into engagement with thecontacts of the next line 1n the group. The alternate operation of thestepping relay 403 and the rotary magnet 412 will continue until an idleline in the group is found or until the switch wipers are rotated intoengagement with the last line in the group. In the latter event if thelast line is busy, since the test contacts similar to 475 and 476 arenot joined together, there will Vbe a ground potential present only uponthe test contact engaged by the test wiper 472. The test relay`406 willbe the only relay operated and a busy tone will be given to the callingsubscriber in the same manner as was described hereinbefore. It will benoted that the slow acting relay 408 maintains the test wiper 472 inconnection with the test relay 406. This circuit renders a very fine andaccurate adjustment of the rotary magnet unnecessary and at the sametime secures a very positive operation. This is for the reason that evenif the test wiper 472 is rotated slightly past the bank contact of theconnected line the slow acting relay 408 maintains it in connection withthe test relay 406 so that the latter relay may deenergize, but if theline is busy it will be again energized upon the switch wipers attainingthelr roper position.

It will now assumed that the line ofthe sub-station A was idle whenconnection therewith was attempted by the connector H. Under thesecircumstances there will be no ground potential resent upon the testcontact 476 'engaged gy the test wiper 472 and no circuit will becompleted for the test relay 406. Then, following the deenergization ofthe slow acting relay 408, a circuit is completed extending from groundon release trunk conductor 381, by way of armature 446 and its backcontact, upper winding of the switching relay 409, back contact andarmature 454, test wiper 472, test contact 476, through the winding ofthe switching relay 480 of the line switch C', and thence through thewinding of the motor magnet 482 to battery. Relays 409 and 480 areenergized over this circuit. However, due to a mechanical interlockingdevice controlled by the armature of the line relay 481 which is nownormal the armatures of the relay 480 are only attracted enough todisconnect the line of the sub-station A from its normal battery andground connections in the line switch C. Relay 409, upon energizing,establishes a locking circuit for itself at armature 461 and atarmatures 457 and 463 completes `the ringing circuit. Ringing current isnow intermittently Projected over the line of the substation A rom thering` ing equipment V.

When the called subscriber answers a circuit for the ring cut oli' relay405 is completed over the called line loop. Relay 405,

upon energizing, establishes a locking circuit for itself at armature441 and at armatures 440 and 442 cuts off the ring and at the frontcontacts of these armatures finally completes the talking connection.The back bridge relay 400 is immediately energized over the line of thesubstation A and supplies talking current to the called subscriber.Relay 400, upon operating, reverses the direction of current flow overthe calling subscribers line. The direction of current iow in the bridgeof the repeater Dis therefore reversed causing the electropolarizedrelays 128 and 132 to operate. Relay 128, upon operating, establishes alocking circuit for itself at armature 163, completes the circuit of theslow acting relay 127 at armature 162, and at armatures. 160 and 164removes its upper winding and the lower winding of the electropolarizedrelay 133 from a bridge across the trunk conductors and also disconnectsthe incoming line conductors 48 and 51 from the windings of the relay135 and the impedance coil 139 and extends them direct to the windingsof the line relay 401 of the connector H. Another result of theenergization of relay 128 is that acircuit is completed extending fromground by way of :front cohtact and armature 161, conductor 49, bankcontact 53, wiper 45, front contact and armature 34, and through thewindmg of the meter magnet 28 to battery. Magnet 28 operates to registerthe completed call .in the usual manner. Relay 127, upon energizing, atits armature 156 completes an additional holding circuit for the lineswitch C, and at armature 155 prepares certain of the coin lcollectcircuits which will be described later. Relay 132 is ,anelectropolarized relay so adjusted `that it will attract its armatureswhen the current is reversed in its upper Winding and will maintain itsarmatures attracted by means of its polarizing vvlnding even if thecircuitoi' its upper winding is opened. However, i the current flow inits upper Winding is restored to normal it will retract its armatures.Relay 132, upon operating, opens a point in the circuit of the relay 131thereby preventing the latter relay from energizing at this time.. rlheup er Winding of relay 132 is included in the ta king circuit but 1sshunted by the non-inductive resistance 193 which affords a path orvoice currents so that the talking eihciency oi the circuit is notmaterially affected.

When the conversation is terminated both subscribers will replace theirreceivers upon their respective switchhooks. When the receiver isreplaced at the calling substation A. the line relay 401 in theconnector H is deenergized as is the slow acting relay 402. The latterrelay, `upon deenergizing, closes apoint in the release circuit of theconnector H at armature 429 and at armature 428 removes ground from therelease trunk conductor 381. By this operation the holding circuits ofthe selector E and E are opened and these switches released. Groundbeing removed from the release trunk conductor 201 the relays 128 and132 in the repeater D are deenergized. Relay 132, upon deenergizing,completes the circuit of the rela-y 131 at armature 175. The latterArelay upon energizing, reverses the trunk conductors 200 and 202 withregard to the conductors of the calling line. This provision is made soas to prevent the line relay 401 from remaining energized Yeven afterthe receiver is replaced at` the substation A` over a circult whichincludes the polarized relay ofthe coin collecting mechanism at thesubstation to ground and the upper winding of the line relav 401,supposing that the called subscriber had hung up before the callingsubscriber. Relay 128, upon deenergizing, opens the circuit of the sloWacting relav 127 but, before this-relay has had time to deenergize, animpulse of current is sent over the following path: ground by Way ofarmature 162 and its back contact, armature 157 and its front contact,and thence through the winding of the slow acting relay 125' to'battery.Relay 125, upon energizing, places an additional ground on the releasetrunk conductor 50 extending back to the line switch C at armature 146,and atthe same armature opens the locking circuit of the slow actingrelay 134 which deenergzes and at armature 147 completes a circuitextending from ground by way of front contact and said armature,conductor 107 and through the Winding of the relay 71 to battery.Another result of the energization of relay 125 is that at armaturesv145 and 144 both sides of 'the line of the substation A are opened andat the front contact of armature 144 the battery lead 105 kfrom thebattery B2 is Aconnected to the line conductor 12 over the closure ofthe above traced circuit current flows from the battery B2 through therelay 140 and the polarized magnet at substation A in series to groundenergizing both the relay 140 and the said magnet. Relay 140 closes atits armature 195 a circuit for the slow acting relay 126. Relay 126,uponenergizing, closes at its armature 149 a circuit for the supervisorylamp L, at its armature 150 completes a locking circuit for the relay127 which, being slow acting, has not yet deenergized, and at armature152 connects the incoming line conductors by Way of the condenser toground. Ordinarily the polarized magnet at substation A will respond atonce to current from battery B2 and will operate to collect thedeposited. coin and restore the entire coin collecting mechanism tonormal condition instantly at the same time disconnecting itself fromline conductor 12. However, it sometimes happens that the armature ofthe polarized magnet will stick and the relay 133 is provided to insurethe collection of the coin in such case. The interrupter I causes vrelay133 to rapidly vibrate its-armature and interrupt the circuit of thebattery B2 'or the battery B in case thisbattery is included in thecircuit with the object of intermittently energizing the polarizedmagnet this operation being ordinarily eii'ective to free the armaturein case it should stick. However, should the armature of the polarizedmagnet continue to stick the relay 126 will remain energized. It will beremembered that vrelay 125, upon energizing, completed a circuitextending from ground by way of front contact and armature 147,conductor 107, through the winding of relay 71 to battery. Relay 71,upon energizing, closes the circuit of the high resistance relay 69 atarmature 91, at armature 93 completes a locking circuit for itself, andat armature 92 closes a circuit which extends over the following path:ground by way of front contact and armature 92, resistance 97, throughthe winding of relay 68 to battery. Relay 68, upon energizing, completesa circuit extending from ground by way of front contact and armature 88,through supervisory lamp L3, through the winding of relay 67, andthrough the winding of relayv 66 to battery. Relay 66 is of such highresistance that the relay 67 is not energized or the lamp Ls lighted inseries withV it-though it receives sulicient current to energize. Relay66, upon operating, completes the circuit of the solenoid 60. Thesolenoid immediately operates to pull up its plunger arm 75. Thisoperation takes considerable time as it is retarded by means of a dashpot. The relay 69, upon ener izing, closed a circuit for the relay 70whici relay energized and opened the locking circuit of the relay 71. Ifthe coin is not collect/ed at the substation A there will still beground resent upon the conductor 107 and the re ay 71 will be maintainedenergized and consequently the solenoid will finally attain its operatedposition. When this occurs the springs 77, 78, and 79 will be forcedinto engagement by the arm 76. When this occurs a circuit is completedeX- tending from battery by way of springs 77 and 78, winding of relay65, windin of relay 67, lamp L8, armature 88 and its ront contact toground. It will be seen that this circuit short circuits the relay 66which deenergizes. The lamp L3 is lit and the relay 67 operated overthis circuit. Relay 67, upon energizing, completes the circuit of thesupervisory lamp L2. The lamp L2 is ageneral supervisory lamp and iscommon to several groups of switches, while the lamp La is individual toa particular group of switches. Relay 67, at its armature 89, alsocloses the circuit of an alarm whereby the attention of the exchangeattendant is attracted. The attendant, upon seeing the lighted conditionof the lamps L2 and L3, will note the nature of the trouble and will goto the particular group of switches designated by the lamp Ls. A lamp Lis individual to each repeater such as D and by the lighted condition ofthis signal the attendant will know it is this particular switch orrather the coin collecting mechanism at the subscribers substation whoseline is as sociated with this switch which is causing trouble.

Another condition that this alarm signal provides for is that in caseeither one of the batteries B or B is out of order the relay 69 will notbe energized and the locking circuit of the relay 71 will be maintainedclosed even though ground is immediately removed from the conductor 107.Therefore the signals LB and L2 will be operated but as there is no lampsimilar to lamp LE5 operated ati this time the exchange attendant willknow the nature ofthe trouble.

Returning now to the operation of the repeater D, when the polarizedmagnet at the .coin collecting mechanism at the calling substation isfinally disconnected from the line, the relay 140 will deener 'ze andopen the circuit of the relay 126 wich relay will deenergize alsothereby opening the locking circuit of the slow acting relay 127. Relay127, upon retracting its armatures, .opens the circuit of relay 125.Relay 125, upon de- .l

energizing, removes groundvfrom the conductor 107 at armature 147, andat armature 146 removes ground from the ,release trunk conductor 50whereby the holding circuit of the switching relay 25 of the line switchC is broken. In this manner all the apparatus is reored to normal and isready for anotherl ca As was previously mentioned, the relay 131 in therepeater D is provided in order to prevent any lockin up of the switcheswhen the called subscrlber at substation A replaced his receiver beforethe calling subscriber. Assuming this to have occurred, the back bridgerelay 400 in the connector H will be deenergized and battery from theline relay 401 will be on the lower heavy talking conductor. The batteryflow over the calling subscribers line is therefore restored to normaland the relay 132 in the repeater D will be deenergized to complete thecircuit of the relay 131. Relay 131, upon energiz ing, reverses theconductors 200 and 201 with regard to the subscribers line in order toprevent the line relay 401 of the connector H from remaining energized,after the calling subscriber hangs up, in series with the polarizedmagnet at the subscribers substation. When the calling subscriber hangsup the release of the connection and collection of the coin will takeplace in the same manner as was before described.

Returning now to the operation of the connector H, it will be assumedthat the calling subscriber at substation A replaces his receiver uponthe switchhook before the called subscriber at substation A does. Theline relay 401 immediately deenergizes and opens the circuit of the slowacting relay 402. Before the deenergization of relay 402 an impulse ofcurrent is sent to' the slow acting relay 408 in series with the slowacting relay 407. However, relay 408 is of such resistance that it onlyis energized over this circuit. Relay 408 operates to remove ground fromthe release trunk 381 for a short interval in order to enable theselectors E3 and E to be released, after which the connector isprotected from seizure immediately upon the deenergization of relay 408,ground being again replaced upon the release trunk 381 through the upperwinding of rela 409. When the called subscriber at substation A' hangsup the back bridge relay 400 is deenergized and the release magnetcircuit closed. The connector H is thus restored to normal by the lastparty to replace his receiver.

In case the called subscriber did not answer it will be necessary toreiund the deposited coin rather than collect it when the callingsubscriber replaces his receiver, and this refunding operation will nowbe explained. Since the called subscriber did not answer neither thepolarized relay 128 nor the polarized relay 132 will be energized and uocircuitI will be completed for the slow acting relay 127 or the metermagnet 28 associated with the line switch of the calling subscriber. Nowwhen the calling subscriber hangs up v his receiver the line relay 135deenergizes and sends an impulse ot current to the slow acting relay 137at thel same time opening the circuit ont the slow acting relay 136. Thelatter relay, upon deenergizing, completes a circuit extending fromround by way of armature 188 and its bac contact, rontcontact andarmature 192, and through the winding oi the slow acting relay 125 tobattery. Upon ener izing, relay 125 operates as before describe exceptthat in the resent case since relay 127 is deenergized t e battery lead106 from the battery Bv is lconnected to the line conductor 12 insteadof the battery B2. Current iow from the battery B now operates relay 140and the polarized magnet at the calling substation in series, the latterbein now actuated to refund the deposited com rather than'collect 1t.Upon energizing, relay 140 completes the circuit of relay 126 whichoperates toh the slow actin close the holdmg circuit of the relay 125.The energization of relay 126 also produces certain other circuitchanges which have been explained before. When the c1rcu1t is finallybroken by the polarized magnet at the calling substation beindisconnected from the line conductor 12 t e relay 140 deener gizes andopens the circuit of relay 126 which deenergizes also. gization of relay126 the holding clrcult of relay 125 is o cned and this relay restoresto normal there y removing ground from the holding conductor 50 and theline switch C 1s thenallowed to restore to normal whereupon all theapparatus will have been released.

Having fully described and ascertalned the features of the inventionwhat is considered to be new and desired to have protected by LettersPatent will be appended claims.

What I claimis': y

1. In a telephone system, a subscribers station, a paystation device atsaid station,

pointed out inthe Vautomatic switches at the exchange, a repeaterinterposed between said line and switches, a control circuit extendingfrom said repeater for operating said switches, and means in certam ofsaid switches for As a result of the deener- ,rendering said controlcircuit inoperative unless a coin has beendeposited in said device'before any of said switches have been operated.

2.. In a telephone s stem, a subscribers station, a paystation evice atsaid station, automatic switches at the exchange, a repeater interposedbetween said line and switches, a control circuit extending from saidrepeater for operating said switches, an operators position accessibleto certain of said switches, a called subscribers line accessible tocertain other of said switches, and means in the said latter switchesonly for rendering said control circuit inoperative unless a coin hasbeen deposited in said device before any of said switches have beenoperated.

3. In a measured service telephone system,

a repeater and associated first selector switch at the exchange, trunklines accessible to said switch each terminating in a second selectorswitch, a release trunk conductor in each trunk line, resistances in therelease trunk conductors extending to certain of said second selectorsonly, and means in said repeater for preventing a calling subscriberfromoperating those selectors whose associated release trunk conductorshave no resistances unless the connection has been paid for before thesaid first selector is operated. A

4. In a telephone system, a subscribers line extending to a centralexchange, coin collecting` mechanism at the station on said line,serially related automatic switches at the exchange, a repeaterinterposed betweenV the said line and switches, a normally operativecontrol circuit extending from the repeater to the first one of saidswitches, means in the lirst switch for extending the control circuit tothe next switch, the extended control circuit being normallyinoperative, means responsive to the deposit of a coin in said mechanismfor rendering said extended control circuit operative, and means forpreventing the deposit of a coin from rendering the extended controlcircuit operative unless the coin is deposited before saidY first switchis operated.

5. In a telephone system, a calling station, a paystation device at thesaid station, selector switches at the exchange, a repeater interposedbetween said line and said switches, a control circuit normallyinoperative extending from said repeater for operating saidselectors,adiiierential relay in -said repeater for rendering said control cir-@ill said trunk line, a release tiunk conductor in said trunk line, acondenser at 'said repeater dividing said release trunk intotwosections, means operated over a calling line for causing theassociated automatic switch to select said trunk line, means in the saidfirst selector for applying ground to one section of the said releasetrunk through a resistance, a relatively low resistance retardationcoil, and means in said repeater for applying ground to the othersection of said re ease trunk through said coil.

7. In a telephone system, a subscribers line, a paystation device on thesaid line, an automatic switch in the exchange, called lines, a repeaterinterposed between said line and switch, means for extending aconnection through said repeater and switch from said subscribers lineto one of said called lines after a coin has been deposited in saiddevice, a battery at the exchange, means in said repeater adapted toimpress current from said battery on the said subscribers line tocollect the coin when the receiver is replaced, a signal, and means foroperating said signal if said battery is out of order at the time thecollection of the coin is attempted.

8. n a telephone system, a subscribers line, a paystation device on thesaid line an automatic switchV in the exchange, called lines, a repeaterinterposed between said line and switch, means for extending aconnection through said repeater and switch from said subscribers lineto one of said called lines after a coin has been deposited in saiddevice, a battery at the exchange, means iii said repeater adapted toimpress current from said battery on the said subscribers line tocollect the coin when the receiver is replaced, a sifgnal, and means:for operating said signal i said coin is not collected by the saiddevice.

9. ln a telephone system, a subscribers line, a paystation device on thesaid line, an automatic switch in the exchange, called lines, a repeaterinterposed between said line and switch, means for extending aconnection through said repeater and switch from said subscribers lineto one of said called lines after a coin has been deposited in-saiddevice, a battery at the exchange, means in said repeater adapted toimpress current from said battery on the said subscribers line\ tocollect the coin when the receiver is replaced, a signal, an-d means foroperating said sigi nal at the expiration of a predetermined timeinterval beginning with the replacement of the receiver in case the coinis not collected in the meantime.

10. In a telephone system, a calling line, a paystation device on thesaid line, a meter for said line, automatic switches in the exchange,called lines, a repeater interposed between said calling line andswitches, a control circuit whereby the subscriber on said calling linemav control said automatic switches to complete a connection to one ofsaid called lines if a coin is de osited in said device, meanscontrolled b t e res nse of the subscriber on said ca ed line oroperating said meter, and'means in said repeater controlled when thesubscriber on said calling line hangs up for collecting said coin.

11. In a telephone system, a calling subscribers station, a calledstation, a paystation device at the said calling station, a trunk lineleading to an automatic switch at the exchange, a repeater included insaid trunk line, means whereby the calling station can extend aconnection to said called station by way of said repeater and switcheswhen a coin as been deposited in the said device, and means in saidrepeater controlled by the subscriber at the called station in replacinghis receiver upon the switchhook for reversing` the conductors of thetrunk extending from said repeater to the automatic switch.

12. In a telephone system, a series of automatic switches for connectinga calling and called line in conversation, means in the final switch forreversing the direction of current flow in the calling line when thecalled man answers, said means being operative only while the receiveris o at the called station. and additional reversing means operatedafter the called man hangs up to maintain the current How in the callingline in the reverse direction.

13. In a telephone system, means including an automatic switchingmechanism for connecting a calling and a called line in conversation, arelay in said mechanism supplying talking current to the calling line, arelay responsive whenthe called man hangs up for reversin the directionof current flow in the calling line, and additional reversing meansoperated when the called man hangs up in order to -prevent such currentreversal.

14. In a telephone system, means includ ing an automatic switchingmechanism for connecting a calling and a called line in conversation, arelay in said mechanism supplying talking current t0 the calling line, arelay responsive when the called man hangs up for reversing thedirection of current flow in the calling line, talking conductors overwhich the talking current is supplied, and means for reversing saidconductors at a point between the calling line and said first relay inorder to maintain the iow of talking current in the same directionnotwithstanding the operation of said second relay.

15. In a telephone system, means including an automatic switchingmechanism for connecting a calling and a called line in conversation, arelay in said mechanism supplying talking current to the calling line, arelay responsive when the called man hangs up lilnece-,eee

ior reversing the direction et current dow in the calling talkingconductors over which the talking current is supplied, a polar relayhaving a winding in one of sai-d conductors and responsive to saidcurrent revernal, and a second reversing relay controlled by said polarrelay for reversing said g conductors a point between the s. polar relayand the calling line.

16. lin a telephone system, a calling line, a paystation thereon,automatic switches at the exchange, a repeater interposed between saidline and said switches, a circuit over which said switches arecontrolled by said repeater in response to a plurality of impulses sentthereto, means or disabling said control cir cuit, a relay, means foroperating sa1d relay to render said disablin means inoperative when acoin is deposited in said paystation, and means tor rendering said relayunresponsive to the deposit of a coin upon the iirst impulse being sentto said repeater.

17; ln a telephone system, a subscribers line, a trunk terminating in anautomatic switch, means for extending said line when calling intoconnection with said trunk, a repeater inserted in said trunk, a releasetrunk conductor in said trunk, a condenser in said release trunkconductor at said repeater dividing said conductor into two inductivelycoupled sections, a `source of tone current associated with said line,means for sending tone current therefrom over said release trunkconductor and through said condenser to said switch, and means forapplying a holding potential to the first section at said repeater tomaintain said line in connection with said trunk, said holding potentialbe ing supplied through a retard coil that prevents said tone currentfrom being shuntedv away from the second section of sa1d release trunkconductora 18. In a telephone system, a subscribers line terminating ina central exchan e, automatic switches accessible to said ine andresponsive .to impulses to extend connections from the calling line toother lines, and means operated to control one of said switchesalsooperated to prevent the init-iated connection being extended beyondcertain of said other switches unless a special act has been previouslyperformed by the subscriber calling, but ineective to prevent aconnection being established via other of said switches.

19. In a telephone system a subscribers line terminating in a centraexchange, automatic. switches accessible to said line and responsive toimpulsesto extend connecill@ tions :trom the calling line to otherlines,

and means operated to control onel of said switches also operated tolinaily determine whether the connection can be extended via any oi saidother switches or whether it can be extended via only certain ci saidother switches.

20. in a telephone system, a calling station, a paystation device at thesaid station, selector switches at the exchange, a repeater interposedbetween. said line and said switches, a. control circuit normallyinoperative extending from said repeater for operating said selectors, adifferential relay in said repeater for rendering said control circuitoperative when a coin is deposited in said device, and means in saidrepeater operative to transmit an operating impulse to one of saidselectors also ei'iective to cause said diderential relay to becomeshort circuited.

21. ln a telephone system, a calling line terminating in a centralexchange, a paystation apparatus at the station of said line, meansincluding a trunk and an automatic switch for setting up a connectionwith called lines of either 'of two classes, a relay included in aseries bridge across the talking conductors of said trunk line, saidrelay` operative contingent on the call being answered and ot aparticular class, and contacts on said relay for causing it todisconnect itself from the bridge and prepare circuits "lli subsequentlyused in collectlng a deposited connecting said release trunk ininductive` relation to the tallnng conductors of the trunk, and means inthe said repeater and 1.10

selector, respectively, for causing the inductively connected current tobe transmitted to the talking conductors of the trunk upon said manuallyoperable means being operated.

In witness whereof, I hereunto subscribe my name this 17th day of May,A. D., 1921.

JOHN W'ICKS.

